To properly fit the \(g^{2}(\tau )\)  correlation function, we measured the instrument response function (IRF) of the system illustrated in Figure 1 of the main text, including the two avalanche photon detectors (APDs) and the time correlated single photon counting card. To record the IRF, the optical filter was removed and the sample was replaced by a blank coverslip. Next, pico-second long pulses of 515 nm wavelength were applied and the response of the APDs was recorded with the time correlation card, following the procedure in Martínez et al.[1]} Figure S1 shows on of our measured response functions. The red curve is a Gaussian fit, where its width, \(\sigma \) , represents the time uncertainty. For our system, \(\sigma = 0.41\)  ns.
